Walking Modulates Speed Sensitivity in Drosophila Motion Vision

Changes in behavioral state modify neural activity in many systems [1–5]. In some vertebrates such modulation has been observed and interpreted in the context of attention [2] and sensorimotor coordinate transformations [3]. Here we report state-dependent activity modulations during walking in a visual-motor pathway of Drosophila. We used two-photon imaging to monitor intracellular calcium activity in motion-sensitive lobula plate tangential cells (LPTCs) in head-fixed Drosophila walking on an air-supported ball. Cells of the horizontal system (HS)—a subgroup of LPTCs—showed stronger calcium transients in response to visual motion when flies were walking rather than resting. The amplified responses were also correlated with walking speed. Moreover, HS neurons showed a relatively higher gain in response strength at higher temporal frequencies, and their optimum temporal frequency was shifted toward higher motion speeds. Walking-dependent modulation of HS neurons in the Drosophila visual system may constitute a mechanism to facilitate processing of higher image speeds in behavioral contexts where these speeds of visual motion are relevant for course stabilization. ► We perform two-photon calcium imaging from optic lobe HS-neurons in walking Drosophila ► The strength of HS response to visual motion is correlated with the fly's walking speed ► Responses to faster moving stimuli are disproportionately strengthened during walking ► Behavioral state changes sensitivity and speed tuning in the fly visual system